1. Field of the Invention
The present invention relates to a semiconductor laser apparatus, more particularly to a semiconductor laser apparatus of an array structure in which two or more semiconductor laser elements are integrally formed on a same substrate hereinafter called a laser array.
2. Description of the Prior Art
Conventional laser arrays have an arrangement as shown in FIG. 1.
FIG. 1 shows a structure involving an array of photodetector elements 93, wherein a laser array 92 and a photodetector array 93 are arranged in mutually opposed positions on a silicon substrate 91. The laser array 92 is bonded to the silicon substrate 91, and the outputs of the lasers 92a-92e are respectively supplied to the photodetectors 93a-93e of the photodetector array 93. The laser array and photodetector array are respectively bonded on the substrate.
The conventional semiconductor laser array discussed above has been associated with the following drawbacks:
(1) Considerable noise is inevitable since each photodetector element not only receives the light from a corresponding laser element but also the light from neighboring laser elements. For example, in FIG. 1, the photodetector element 93b naturally receives its largest input of light from the laser element 92b, but it also receives considerable light from the laser elements 92a, 92c etc. For this reason it is difficult to simultaneously detect the inputs from the laser elements 92a-92e without mutual interference.
(2) It has been difficult to position the different elements of the laser array in a position exactly corresponding to the elements of the photodetector array, on the substrate.